Segmentation of sperms using the strategic Hough transform.

A new method based on the Hough transform has been used for the quantitative estimation of the morphological characteristics of the sperm. Images of the sperms were acquired into the digital format using the optical microscope, CCD camera, and frame grabber. For each sperm in the image, the region of interest for the segmentation of the sperm head was selected using the density difference between the sperm head and background. The boundary of the sperm head was approximated with an ellipse and represented by five parameters. These five parameters representing an ellipse have been investigated by applying the Hough transform strategically. During the searching procedure using the Hough transform, we restricted the searching volume minimally and moved the next searching volume to the direction showing the steepest gradient of the estimation error. Also, we increased the parameter resolution from the three pixel distance to the one pixel distance. For the tested images, head boundaries of the sperms were estimated with an error of 1/2 pixel distance, and morphological parameters were calculated by the equations without further image processing. This new method separates sperm head based on the geometrical characteristic of the sperm and calculates morphological parameters simply from the derived boundary.